Examining the Impact of Later High School Start Times on the Health and Academic Performance of High School Students: A Multi-Site Study - Adolescents should start the school day no earlier than 8:30 in order for them to get eight, preferably nine hours sleep for maximum neural development, say the authors of this report. Teens who got that much sleep were less likely to report being depressed or using caffeine or other substances. Also, there was a reduction in local car crashes, less absenteeism, less tardiness and higher achievement test scores. Maintenance of the status quo was the strongest force against a later start time. (Kyla L. Wahlstrom, et al., Center for Applied Research and Educational Improvement, March 2014)...